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  • 1
    Electronic Resource
    Electronic Resource
    The fine structure of the buccal tentacles of Holothuria forskali (Echinodermata, Holothuroidea) (1982)
    Springer
    Zoomorphology 101 (1982), S. 133-149 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ultrastructural study of the buccal tentacles of Holothuria forskali revealed that each tentacle bears numerous apical papillae. Each papilla consists of several differentiated sensory buds. The epidermis of the buds is composed of three cell types, i.e. mucus cells, ciliated cells, and glandular vesicular cells (GV cells). The GV cells have apical microvilli; they contain bundles of cross striated fibrillae associated with microtubules. Ciliated cells have a short non-motile cilium. Bud epidermal cells intimately contact an epineural nervous plate which is located slightly above the basement membrane of the epidermis. The epineural plate of each bud connects with the hyponeural nerve plexus of the tentacle. This nerve plexus consists of an axonic meshwork surrounded in places by sheath cells. The buccal tentacles have well-developed mesothelial muscles. Direct innervation of these muscles by the hyponeural nerve plexus was not seen. It is suggested that the buccal tentacles of H. forskali are sensory organs. They would recognize the organically richest areas of the sediment surface through the chemosensitive abilities of their apical buds. Tentacles presumably trap particles by wedging them between their buds and papillae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312019
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  • 2
    Electronic Resource
    Electronic Resource
    Functional morphology of the pedicellariae of the asteroid Marthasterias glacialis (Echinodermata) (1984)
    Springer
    Zoomorphology 104 (1984), S. 122-130 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Marthasterias glacialis bears two kinds of pedicellariae. The straight pedicellariae are single and occur everywhere on the asteroid body surface except in the ambulacral groove. The crossed pedicellariae are clustered on mobile structures (the rosettes) build around marginal and abactinal spines. Basically, each pedicellaria has a head and a stalk. A skeleton occurs only in the pedicellarial head. It consists of two valves and a basal piece. Muscular bundles are anchored on these skeletal ossicles. The straight pedicellariae have two pairs of adductor muscles (the inner and the outer adductors) and one pair of abductor muscles, these latter being weakly developed. Longitudinal muscle fibers occur all along the stalk of straight pedicellariae. The crossed pedicellariae have two pairs of adductor muscles (the distal and the proximal adductors) and two pairs of abductor muscles (the distal and the proximal abductors). The proximal adductors of crossed pedicellariae are homologous to the stalk muscles of straight pedicellariae. The pedicellariae are able to react to direct and indirect tactile stimuli. There is a great deal of individual variation among pedicellarial responses. Moreover, the reactions occur at random and lack coordination. The seemingly aberrant behavior of the pedicellariae is interpreted as a preventive activity that protects the asteroid body surface against unwanted materials and organisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312026
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  • 3
    Electronic Resource
    Electronic Resource
    The skeleton of the stalked stages of the comatulid crinoid Antedon bifida (Echinodermata) (1987)
    Springer
    Zoomorphology 107 (1987), S. 58-65 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cystidean calyx of Antedon bifida (Pennant, 1777) consists of two superposed series of five inter-radially located plates called basals (lower plates) and orals (upper plates). A single radianal and five radial plates develop in early pentacrinoids. They are radially located between the orals and the basals and alternate with them. During pentacrinoid life, radials grow continuously while orals progressively regress. Basals fuse to the proximal forming the so-called rosette, and the radianal grows till the anal cone is formed and then regresses. The first primibrachials arise in 25 day pentacrinoids. Arms of detached juveniles usually have 13 secundibrachials, with IIBr13 each having a developing pinnule. No infrabasal develops between the series of basals and the upper columnal. During pentacrinoid life, the stalk progressively changes from homeomorphic to xenomorphic while most columnal articulations change from symmorphies to synarthries. Synarthrial fulcral ridges can rotate about 60° from one columnal articulation to another, allowing the stalk to be flexible in every direction. Formation of new columnals is continuous until the proximal appears (i.e. in 65 day pentacrinoids). The number of columnals in the fully-formed pentacrinoid stalk varies from 17 to 24 depending on the individual. Developing cirri are seen in 70 day pentacrinoids. Detached juveniles have two well-developed series of five cirri, which usually consist of ten cirral ossicles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312130
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  • 4
    Electronic Resource
    Electronic Resource
    Functional morphology of the tentacles and tentilla of Coeloplana bannworthi (Ctenophora, Platyctenida), an ectosymbiont of Diadema setosum (Echinodermata, Echinoida) (1997)
    Springer
    Zoomorphology 117 (1997), S. 165-174 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The tentacular apparatus of Coeloplana bannworthi consists of a pair of tentacles which bear, on their ventral side, numerous tentilla. Each tentacle extends from and retracts into a tentacular sheath. Tentacles and tentilla are made up of an axial core covered by an epidermis. The epidermis includes six cell types: covering cells, two types of gland cells (mucous cells and granular gland cells), two types of sensory cells (ciliated cells and hoplocytes), and collocytes, this last cell type being exclusively found in the tentilla. The core is made up of a fibrillar matrix, the mesoglea, which is crossed by nerve processes and two kinds of smooth muscle cells. Regular muscle cells are present in both the tentacles and tentilla while giant muscle cells occur exclusively in the tentilla. The retraction of the tentacular apparatus is an active phenomenon due to the contraction of both types of muscle cells. The extension is a passive phenomenon that occurs when the muscle cells relax. Tentacles and tentilla first extend slightly due to the rebound elasticity of the mesogleal fibers and then drag forces exerted by the water column enable the tentacular apparatus to lengthen totally. Once the tentacles and tentilla are extended, gland cells, sensory cells, and collocytes are exposed to the water column. Any swimming planktonic organism may stimulate the sensory cilia which initiates tentillum movements. Pegs of hoplocytes can then more easily contact the prey which results in a slight elevation of the nearby collocytes, the last being responsible for gluing the prey to the tentilla.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004350050041
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  • 5
    Electronic Resource
    Electronic Resource
    Fine structure and presumed functions of the pedicellariae of Echinocardium cordatum (Echinodermata, Echinoida) (1987)
    Springer
    Zoomorphology 106 (1987), S. 279-288 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Tridactylous, trifoliate, and globiferous pedicellariae occur on the body surface of Echinocardium cordatum. Tridactyles have three forms: the typical, the rostrate, and the large forms. Both typical and rostrate tridactyles and trifoliates occur all around the echinoid body (trifoliates are, however, 4 times more numerous than tridactyles). Large tridactylous and globiferous pedicellariae are restricted to the peribuccal area. As a general rule tridactyles and trifoliates are similar in morphology. The distal part of the valves forms an open blade and bears lateral teeth and/or denticles (single or in combs). The stalk consists of a rigid proximal part supported by an axial rod and a flexible distal part which includes an axial fluid-filled cavity. The cavity is surrounded by muscle fibers and acts as an hydroskeleton, allowing the undulating-coiling movements of the flexible part of the stalk. Trifoliates are always active while tridactyles react only to direct or indirect mechanical stimulation. The valves of the globiferous pedicellariae have a tubular distal part whose upper opening is surrounded by teeth. There is no differentiated venom gland but a cluster of epithelial glandular cells located at the level of the valve upper opening. A small ciliary pad occurs just below the glandular cluster. Globiferous stalks are not flexible, being supported for their full length by an axial rod. Globiferous pedicellariae appear to be sensitive only to chemical stimulation. The presumed functions of E. cordatum pedicellariae are (1) cleaning of the body surface and ciliary structures (trifoliates), (2) protection against sedimenting particles (tridactyles), and (3) defense of the peribuccal area against potential small predators (globiferous pedicellariae).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312002
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  • 6
    Electronic Resource
    Electronic Resource
    Functional morphology of vibratile urnae in the synaptid holothuroid Leptosynapta inhaerens (Echinodermata) (1989)
    Springer
    Zoomorphology 109 (1989), S. 165-171 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Vibratile urnae of Leptosynapta inhaerens are organized in three longitudinal bands along the mesenteries. An individual of 10 cm length usually houses about 4500 urnae. These are minute (300 Gmm high), S-shaped and hollow peritoneal organs consisting of an intracoelomic projection of the body wall mesothelium supported by a thin connective tissue layer. The urnal cavity is strongly ciliated. Each urna harbours a clump of coelomocytes at the lower part of its aperture. The clump is attached to the urna through spot-like desmosomes occurring between its inner-most coelomocytes and apical urnal cells. Clumps and urnae form functional units. Urnal cilia produce steady water currents through urnal cavities and whirls along urnal bands. The particulate material conveyed by the coelomic fluid enters the urnal cavity and is either trapped by coelomocyte pseudopodia or agglutinated by a mucoid substance that covers the clump's outer surface. Depending on individuals, clearance of coelomic fluid occurs from 2 to 3 h after experimental injection of particulate material. The effectiveness of coelomic fluid clearance appears to be due to the particular organization and location of urnae, viz. in longitudinal bands along the mesenteries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312268
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructure of the tube foot sensory-secretory complex in Ophiocomina nigra (Echinodermata, Ophiuridea) (1990)
    Springer
    Zoomorphology 109 (1990), S. 201-209 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of the epidermal layer of both the oral and arm podia of the brittle star Ophiocomina nigra is described. Despite external differences, little variation occurs in their internal structure. The podial epidermis, which is overlain by a three-layered cuticle, consists of five cell types: support, mucous, sensory, adhesive secretory and monociliated ‘neurosecretory-like’ cells. Areas of specialisation are superimposed on this basic plan. These comprise four cells forming cohesive units, made up of two adhesive secretory, one sensory and one monociliated ‘neurosecretory-like’ cells. The two adhesive secretory cells may be identical or vary in the structure of their secretory packets. The sensory cells are of the normal type bearing a short cilium with a 9+2 microtubular arrangement. The monociliated ‘neurosecretory-like’ cells contain many small dense vesicles and a short sub-cuticular cilium of irregular microtubular structure. Together, they appear to form a sensory-secretory complex which functions in adhesion both for feeding and locomotion. A system in which the secretion of the monociliated ‘neurosecretory-like’ cell may control adhesive secretion is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312471
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  • 8
    Electronic Resource
    Electronic Resource
    Functional morphology of the locomotory podia ofHolothuria forskali (Echinodermata, Holothuroida) (1992)
    Springer
    Zoomorphology 111 (1992), S. 167-178 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ventral surface ofHolothuria forskali (Holothuroida, Aspidochirotida) is almost completely covered by small-sized podia that are locomotory. Each podium consists of a stem that allows the podium to lengthen, to flex, and to retract, and this is topped by a disc that allows the podium to adhere to the substratum during locomotion. Podia ofH. forskali do not end in a sucker and their adhesion to the substratum thus relies entirely on the disc epidermal secretions. The disc epidermis is made of five cell types: non-ciliated secretory cells of two different types that contain granules whose content is either mucopolysaccharidic (NCS1 cells) or mucopolysaccharidic and proteinic in nature (NCS2 cells), ciliated secretory cells containing small granules of unknown nature (CS cells), cilitated nonsecretory cells (CNS cells), and support cells. The cilia ofCS cells are subcuticular whereas those ofCNS cells, although also short and rigid, traverse the cuticle and protrude in the outer medium. During locomotion, epidermal cells of the podial disc are presumably involved in an adhesive/de-adhesive process functioning as a duogland adhesive system. Adhesive secretions would be produced byNCS1 andNCS2 cells and de-adhesive secretion byCS cells. All these secretions would be controlled by stimulations of the two types of ciliated cells (receptor cells) which presumably interact with the secretory cells by way of the nerve plexus. The lack of suckers and the coexistence of two adhesive cell types in the disc epidermis give the locomotory podia ofH. forskali a “compromise” structure which would perhaps explain their ability to move as efficiently along soft and hard substrata.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01632906
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  • 9
    Electronic Resource
    Electronic Resource
    Functional morphology of coronal and peristomeal podia in Sphaerechinus granularis (Echinodermata, Echinoida) (1993)
    Springer
    Zoomorphology 113 (1993), S. 47-60 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Coronal podia of Sphaerechinus granularis are anchoring (adhering) appendages involved in either locomotion or capture of drift materials. Adhesion is not due to the presumed sucker action of the disc but relies entirely on secretions of the disc epidermis. Peristomeal podia function in wrapping together food particles or food fragments in an adhesive material thus facilitating their capture by the Aristotle's lantern. In both types of podia, the disc epidermis is made up of four cell types: non-ciliated secretory cells (NCS cells) that contain graules whose content is at least partly mucopolysaccharidic in nature, ciliated secretory cells (CS cells) containing granules of unknown nature, ciliated non-secretory cells (CNS cells) and support cells. The cilia of CS cells are subeuticular whereas those of CNS cells, although also short and rigid, traverse the cuticle and protrude in the outer medium. All these cells are presumably involved in an adhesive/de-adhesive process functioning as a duogland adhesive system. Adhesive secretion would be produced by NCS cells and de-adhesive secretion by CS cells. These secretions would be controlled through stimulations by the two types of ciliated cells (receptor cells) which presumably interact with the secretory cells by way of the nerve plexus. This model of adhesion/de-adhesion fits well with the activities of both coronal and peristomeal podia. The secretion of NCS cells would make up a bridge of adhesive material between a podium and the substratum (coronal podia) or would coat and gather food particles (peristomeal podia), respectively. The de-adhesive material enclosed in the granules of CS cells would allow the podia (either coronal or peristomeal) to easily become detached from the substratum and to always remain clear of any particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00430976
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  • 10
    Electronic Resource
    Electronic Resource
    Occurrence of a microcanalicular system within the ossicles and dermal tissue of Asterias rubens and Marthasterias glacialis (Echinodermata: Asteroidea) (1985)
    Springer
    Cell & tissue research 242 (1985), S. 657-660 
    Details
    ISSN: 1432-0878
    Keywords: Ossicle ; Dermis ; Epithelium ; Mesoderm ; Echinodermata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A microcanalicular network is demonstrated within the ossicle stroma and the dermal tissue of two asteroid species. Microcanaliculi are presumed to be mesodermal structures. They consist of convoluted tubular ducts lined by epithelial cells associated with scattered basiepithelial nervous processes. Such a microcanalicular system has not been reported previously from any echinoderm species. Its discovery in asteroids entails some conceptual changes, especially considering the physiology of the body wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225434
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